Method for conditioning rotatable grinding wheels



Feb. 13, 1951 I w. w. BROUGHTON 2,541,912

METHOD FOR CONDITIONING ROTATABLE GRINDING WHEELS Filed June 18, 1947FIGJ.

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U [mg n nnn 22 EIHIHIHIIEI [:HIHIJEI] nuu n nun IN VENTOR W. W.BROUGHTON A TTORNEY Patented Feb. 13, 1951 UNITED STATES TNT OFFICEMETHOD FOR EONDITIONING ROTATABLE GRINDING W'HEELS York Application June18, 1947, Serial No. 755,399

6 Claims.

This invention relates to a method of conditioning rotatable grindingwheels, more particularly diamond grinding wheels employed in -grind ingquartz crystals or the like.

Various methods and apparatus are employed in producingwafer-like'structures fro-m quartz crystals beginning with the motherstone and ending with the final wafer suitable for use in quartz crystalfilters and other electrical units. The method of particular interestincludes the use of a rotatable grinding wheel commercially known as adiamond grinding wheel, containing diamond particles embedded in a baseof softer material, employed to grind quartz crystal members to giventhicknesses. The crystals to be ground are cemented to one or moremounting plates di, posed upon a rotatable unit, such as a magneticchuck, rotated about its axis relative to a rotatable grinding wheel. Ithas been necessary to recondition the rinding wheel after each grindinoperation to sharpen the wheel by removing quantities of the basematerial and exposing diamond particles for the next grinding operation.

I Heretofore, the reconditioning or sharpening process was carried outby the aid of a carborundum stick held against the face of the grindingwheel while rotating, but positioned away from the chuck and mountingplates. The reconditioning operation was thus left to the discretion ofthe operation and when the crystals were ground 1 on a piecework basis,it was the tendency for the operator to apply the carborundum stick fora longer interval of time than was necessary to sharpen the grindingwheel, in an attempt to make the wheel extra sharp to shorten the time3':

for grinding the crystals to their required thickness. As a result, theuseful life of the grinding wheel was greatly shortened and its grindingaction was made non-uniform by irregular sharpening of the wheel due tothe application of the carborundum stick at certain portions of thegrinding wheel for longer intervals of time than at other portionsthereof.

The object of the present invention is to eliminate excessreconditioning wear of grinding wheels by the use of a methodwh-ichremoves only the required quantity of base material and maintains thegrinding wheel uniformly sharp.

With this and other objects in view the invention comprises the methodof conditioning rotatable grinding wheels for grinding articles. Theapparatus includes an abrasive member and a mounting element, for boththe abrasive member and the article to be ground, mounted on a supportand movable relative to "the grinding wheel.

2 The method includes the step of mounting an abrasive member on thesupport with the article to engage the grinding wheel during relativemovement of the support and grinding wheel to condition the grindingwheel during grinding of the article.

In the present embodiment of the invention, carb'orundum wafers, greaterin thickness than the initial thickness of the articles or quartzcrystal members, are cemented on mounting plates with the articles atspaced positions whereby all surfaces of the grinding wheel will beengaged by the wafers durin grinding operation. The mounting plates arepie-shaped in general contour and are disposed upon a magnetic chuckWhere they are held during rotation of the chuck about its axis. Theaxis of the chuck is offset from the axis of the grinding wheelandparallel therewith whereby the articles, together with the wafers aremoved to be engaged by the grinding wheel. The grinding wheel has agiven downward pressure to first engage the carborundum wafers and bereconditioned'thereby prior to the engagement of the grinding wheel withthe articles, the carborundum wafers continuing to recondition thearticles during the grinding operation reducing them to their giventhickness.

Other objects and advantages will be apparent from the followingdetailed description when considered in conjunction with theaccompanying drawing, wherein Fig. 1 is a fragmentary front elevationalview of the grinding apparatus by the aid of which the method may bepracticed;

Fig. 2 is a top plan view of the magnetic chuck with the mounting platesdisposed thereon;

Fig. 3 is a fragmentary detailed view of a portion of the grindingwheel;

Fig. 4 is a perspective view of one of the conditioning wafers prior tomounting on the mountin'g plate;

Fig. 5 is a perspective view of one of the wafers at the completion ofthe grinding operation; and

Fig. 6 is a perspective view of a carborundum stick as employed in theformer reconditioning method Referring now to the drawing, the apparatusincludes a magnetic chuck Hi supported on avertical shaft H for rotationin agiven direction about the vertical axis of the shaft.

' Mounting plates l2 are pie-shaped in general contour whereby one, two,three or-four of them may be disposed upon the magnetic chuck for thegrinding of articles M. In the present embodimerit-of the invention, thearticles M are quartz crystal members which are to be reduced inthickness to a given dimension.

The grinding wheel mounted for rotation with its shaft l6, the axis ofwhich is spaced from, but parallel with the shaft H, is employed togrind the articles to their given thickness. In the present embodimentof the invention, the grinding wheel is of the diamond type, including amultiplicity of diamond particles 18 embedded in a base or supportingmaterial 19. During grinding operations upon quartz crystals or othersimilar materials, the diamond grinding wheel becomes dull and must besharpened to increase its effectiveness by periodically removingportions of the base material to expose the diamond particles and tothus sharpen the grinding wheel. Heretofore the sharpening orconditioning operation has been accomplished by the aid of a carborundumstick 2e forced manually against the face of the grinding wheel.

This method had its unsatisfactory results, first in producing irregularsharpening of the wheel, and the rapid wearing away of the .wheelunnecessarily to greatly reduce its effective life.

The present apparatus includes wafers 22, formed of abrasive materialssuch as carborundum, mounted at spaced positions on the various supports[2 whereby all portions of the face of the grinding wheel will beengaged by the wafers prior to and during the grinding operation. Itwill be observed by viewing Fig. 1 that the conditioning wafers 22 arethicker than the initial thickness of the articles 14 whereby the faceof the grinding wheel will be conditioned removing portions of the basematerial H] from the grinding wheel to expose diamond particles l8 andto thus sharpen the grinding wheel before it meets the articles I4 tobegin the grinding operation thereof. Furthermore, the grindingoperation is shortened by the constant conditioning of the'grindingwheel during the grinding operation. Although the wafers 22 are grounddown to the initial thickness of the articles M in their initialconditioning step, they continue to condition the face of the grindingwheel as the articles are ground to their desired thickness.

In this manner, excess materials are not removed from the grinding wheeland the time previouslyrequired for conditioning the grinding wheel isgreatly reduced. All that is required of the operator is the mounting ofthe wafers 22 at scattered positions on the mounting plates l2 among thearticles I a which are to be ground. The wafers remaining upon themounting plates at the completion of the grinding operation may beremoved with the articles and when an additional supply of articles onmounting plates are disposed upon the chuck IE! with the desired numberof wafers 22 selectively positioned on the supporting plates, no time islost for conditioning the grinding wheel in that it is conditionedduring its movement toward the articles.

Although specific improvements of the invention have been shown anddescribed, it will be understood that they are but illustrative and thatvarious modifications may be made therein without departing from thescope and spirit of this invention as defined by the appended claims.

What is claimed is:

1. The method of conditioning rotatable grinding wheels for grindingarticles disposed on a mounting element of a support therefor movablerelative to the grinding wheel, the method comprising mounting anabrasive member on the mounting element with the article to engage thegrinding wheel during relative movement of the support and grindingwheel to condition the grinding wheel during grinding of the article.

2. The method of conditioning rotatable diamond grinding wheels forgrinding articles, such as quartz crystals, disposed on a mountingelement of a support therefor movable relative to the grinding wheel,the method comprising mounting an abrasive member on the mountingelement with the article to engage the grinding wheel during relativemovement of the support and grinding wheel to condition the grindingwheel during grinding of the article.

3. The method of conditioning rotatable diamond grinding wheels forgrinding articles, such as quartz crystals, disposedon a mountingelement of a support therefor movable relative to the grinding wheel,the method comprising mounting an abrasive member thicker than thearticle on the mounting element with the article to engage the grindingwheel during relative movement of the support and grinding wheel tocondition the grinding wheel prior to and during grinding of thearticle.

4. The method of conditioning rotatable grinding wheels, composed mainlyof diamond particles in a molded bindin material, for grindingparticles, such as quartz crystals, disposed on a mounting element of asupport therefore movable relative to the grinding wheel, the methodcomprising mounting an abrasive member on the mounting element with thearticle to engage the grinding wheel during relative movement of thesupport and grinding wheel to remove portions of the binding material ofthe grinding wheel during grinding of the article to maintain thediamond particles exposed to the article.

5. The method of conditioning rotatable grinding wheels, composed mainlyof diamond particles in a molded binding material, for grindingarticles, such as quartz crystals, disposed on a mounting element of asupport therefor movable relative to the grinding wheel, the methodcomprising mounting an abrasive member thicker than the article on themounting element with the article to engage the grinding wheel duringrelative movement of the support and grinding wheel to remove portionsof the binding material of the grindin wheel prior to its engagementwith the article and during grinding of the article to maintain thediamond particles exposed to the article.

6. The method of conditioning a movable grinding element for grindingarticles disposed on a mounting element of a support therefor movablerelative to the grinding element, the method comprising mounting anabrasive member on the supporting element with the article to engage thegrindin element during relative movement of the support and the grindingelement to condition the grinding element during grinding of thearticle.

WILLIAM W. BROUGHTON.

REFERENCES orrsn The followingreferences are of record in the file ofthis patent:

UNITED STATES PATENTS Briney Mar. 28, 1944

